1. Field of the Invention
This invention relates to removal of waste liquid from an automated instrument, more particularly, an automated instrument that employs a variety of liquids.
2. Discussion of the Art
The ARCHITECT® family of automated diagnostic instruments requires fluid handling systems that employ at least one sub-system for aspirating and dispensing samples and reagents, at least one sub-system for dispensing buffers, at least one sub-system for dispensing pre-trigger fluids and trigger fluids, and at least one sub-system for handling liquid waste.
Through the aspiration process, samples are moved from sample containers and assay reagents are moved from reagent bottles for dispensing into reaction vessels. In addition, wash buffer is dispensed for priming and flushing. Trigger solutions and pre-trigger solutions are also dispensed into reaction vessels.
Pipette probes, together with syringes and valves, are used to aspirate reagents from reagent bottles and dispense them into a reaction vessel. A pipette probe is used to aspirate a sample from a sample container and dispense it into a reaction vessel. Fluids are aspirated through the pipette probe(s) by a syringe and then dispensed in the same manner by reversing the direction of travel of the syringe plunger. A system of robotics positions pipette probe(s) to the appropriate bottle, container, or reaction vessel for the aspiration and dispensing process steps. The pipette probes that handle reagents are washed with wash buffer in active wash cups. The pipette probe that handles samples is washed with wash buffer in a passive wash cup. Wash zones for washing the microparticles and the inside surfaces of the reaction vessels comprise a manifold having dispensing nozzles and valves. At the wash zones, wash buffer is dispensed into reaction vessels and liquid is aspirated from reaction vessels. A waste aspiration probe is used to aspirate liquid from a reaction vessel prior to discarding the reaction vessel to solid waste.
Waste liquid in the ARCHITECT® i2000SR instrument is removed by a system of drains that relies on the principle of gravity. This system requires the use of so-called “vacuum vessels” and solenoid drain valves at each of the active wash cups and microparticle wash stations. A liquid waste management system based on that used in the ARCHITECT® i2000SR instrument is shown schematically in FIG. 1. The system 10 includes two vacuum vessels 12 and 14, vacuum vessel 12 having solenoid valves 16a and 16b associated therewith and vacuum vessel 14 having solenoid valves 18a and 18b associated therewith. A wash cup 20 is associated with the washing process for the sample probe and a wash cup 22 is associated with the washing process for the reagent probe. The waste liquid flows by gravity into a gutter system 24, which is open to the environment at several collection points, i.e., the collection point 24a from the wash cup 22 for waste liquid from the sample probe wash, the collection point 24b from the wash cup for waste liquid from the reagent probe wash, the collection point 24c from the CMIA (Chemiluminescent Microparticle Immunoassay) washer 26, the collection point 24d from the pre-trigger fluidics, the collection point 24e from the trigger fluidics, and the collection point 24f from the microparticle wash zone.
Vacuum is supplied to the ARCHITECT® i2000SR instrument for the CMIA wash process to extract wash fluid waste from the system. Vacuum is also supplied to the reagent probe wash station to dry the probe after the probe has been washed in the wash cup 22. Vacuum is used to aspirate liquid from the reaction vessels.
The vacuum system consists of an accumulator assembly 28, vacuum vessel assemblies comprising (a) the vacuum vessel 12 and solenoid valves 16a and 16b and (b) the vacuum vessel 14 and solenoid valves 18a and 18b and a vacuum pump 30 with a filter 32. The accumulator assembly 28 comprises an accumulator 28a, a vacuum switch 28b, and a liquid level sensor 28c. The vacuum system is used to supply vacuum to the active wash cup(s) 22, wash zone aspiration probes 34a, 34b, 34c and waste aspiration probe (not shown). Solenoid valves 16a and 18a are opened, allowing the vacuum to suction liquid from the reaction vessels or the wash cup 22. The liquid is drawn into a liquid separation vessel 12 and 14 where it is held until the vacuum cycle is complete. When the vacuum cycle is complete, the solenoid valve to the reaction vessel (solenoid valve 18a) or wash cup (solenoid valve 16a) close, the solenoid valves 16b and 18b to the drain open, and the liquid drains into the gutter system 24 by gravity. The liquid waste is distributed to a waste manifold 38, which can be connected to an external liquid waste floor drain 40, a waste pump (not shown), or a container (not shown). The fluid lines shown in FIG. 1 are typically made of flexible tubing, ¼-inch inside diameter for the waste removal area 44, and 1/16-inch inside diameter for the microparticle wash zone 26. The diameter(s) of such tubing is (are) readily determinable by one of ordinary skill in the art.
The liquid waste management system shown in FIG. 1 has certain drawbacks. One drawback involves excessive space requirements and, consequently, excessive cost, relative to a system that has only one wash cup, no vacuum vessel, and no gutter system. The gutter system 24 shown in FIG. 1, being open to the environment, can collect dust and other foreign objects inadvertently dropped into it. Such debris can result in a blockage of flow of liquid. Furthermore, the gutter system 24 is difficult to clean. In a system operating by gravity induced flow, the rate of flow of the waste liquid is determined by the relative height of the liquid with respect to the destination of the fluid and the flow resistance of the solenoid valves, tubing, and connections. For example, the height of the liquid in the vacuum vessels 12 and 14 is less than two inches above the solenoid valves 16b and 18b. This height differential corresponds to a pressure difference of about 0.072 psi across the solenoid valves 16b and 18b. As the pressure difference increases, the liquid can be moved in a shorter period of time and will have a wider margin for the evacuation time if the resistance to flow were to increase over time. The pressure differential available solely through the force of gravity with the ARCHITECT® i2000SR instrument is very small. Vacuum provides a much higher pressure differential and, consequently, a much higher rate of fluid flow. Accordingly, a given volume of liquid can be evacuated with in a shorter period of time. In automated analytical instruments, events are scheduled in a tight sequence. If waste liquid is not removed before the valve to the drain is scheduled to be closed, waste liquid will progressively accumulate. Higher flow rates are likely to keep the conduits for the flow of fluid cleaner. Another drawback of the system of drains based on gravity induced flow is that the laboratory drain 42 into which the waste liquid ultimately flows has to be at a lower level than the floor (not shown) on which the automated diagnostic instrument stands.
The wash cups 20 and 22 in the ARCHITECT® i2000SR instrument are used to clean the pipette probes by washing the probes after each use thereof. A passive wash cup 20 is used to wash the pipette probe that handles the sample. An active wash cup 22 is used to wash the pipette probe that handles the reagent. These wash cups 20 and 22 will not facilitate the wash protocols that are to be used on a modification of the ARCHITECT® i2000SR instrument that uses only one wash cup. This modification of the ARCHITECT® i2000SR instrument will not require a separate wash pump. Furthermore, this modification of the ARCHITECT® i2000SR instrument will be required to provide clean buffer for aspiration by the probe.
The liquid waste management system of the ARCHITECT® i2000SR instrument does not allow for the use of an on-board liquid waste container. Accordingly, removal and replacement of an on-board liquid waste container while the instrument is operating is not possible.
The liquid waste management system based on the ARCHITECT® i2000SR instrument does not have an on-board liquid waste pump. Thus, the system cannot pump the liquid waste to laboratory drains that are at a level higher than the floor on which the automated diagnostic instrument stands.
The liquid waste management system of the ARCHITECT® i2000SR instrument does not have a pressure sensor in the liquid waste outlet to sense any obstruction to the flow of liquid waste. Obstruction of the flow of liquid waste in the ARCHITECT® i2000SR instrument can lead to liquid spills, which, of course, can lead to undesirable conditions.
The vacuum pump used in the ARCHITECT® i2000SR instrument is driven by an alternating current (AC) motor at a relatively constant speed. The pump is not designed to allow for feedback control of the level of vacuum by matching the pump speed to the flow demand.
Another automated diagnostic instrument currently available is the ACCESS system, commercially available from Beckman Coulter Incorporated. The on-board liquid waste container of the ACCESS system can be removed for only a short time while the ACCESS instrument is running. Either an empty liquid waste container has to be connected immediately, or a pan must be provided to collect the liquid waste. Accordingly, it would be desirable to develop a liquid waste removal system that allows removal and replacement of an on-board liquid waste container, even while the automated diagnostic instrument is operating. It would also be desirable to develop a liquid waste removal system that allows for an optional connection to a laboratory drain. It would be further desirable to develop a liquid waste removal system for an automated diagnostic instrument that utilizes an accumulator, which can also serves as a temporary waste liquid storage container to minimize the number of components in the system, thereby reducing cost and space requirements.